I've used tolulene, xylene, and MEK (methyl ethyl ketone). All are similar in usage as solvents. We used them in our paint department as thinner and cleaning agents for our epoxy and bake-on paints. It will dry your skin out quickly.
I used to get a couple of gallons of the tolulene, with permission from my boss, on race weekends to use as an octane booster (was also used as full racing fuel years ago, but they stopped due to fuel system problems and cylinder wear from lack of lubricity). As long as you mix it properly at the right ratio, it still works as an octane booster.
I had a separate ten gallon fuel tank in the bed of my S-10 (with a 327 SBC V-8 under the hood) that I used when racing. After I got to the track, I closed a valve on the regular tank and opened the valve to the race tank. It had a mix of 80% 97 octane pump gas and 20% tolulene which should run around 101-104 octane. I changed plugs, bumped the timing, and swapped jets in the carb and it was ready to roll. I came out cheaper than the $4.00 per gallon for 104 racing gas at the track (this was 1991-92).